1441 patients with IDDM - 726 with no retinopathy at base line (primary-prevention cohort) and 715 with mild retinopathy (secondary-intervention cohort) were randomly assigned to intensive therapy administered either with an external insulin pump or by 3 or more daily insulin injections and guided by frequent daily insulin injections. The patients were followed for a mean of 6.5 years, and the appearance and progression of retinopathy and other complications were assessed regularly.